• MIT researchers have built a tiny magnetic mixer that keeps cells evenly suspended during extrusion bioprinting, looking to make printed tissues far more repeatable. • Extrusion 3D bioprinting typically uses syringes to deposit soft hydrogels loaded with living cells, and it tends to run into an unglamorous but persistent problem: gravity. • Cells are typically denser than the gel around them, so during longer print jobs they sink inside the syringe. • Over time that can change the “recipe” coming out of the nozzle, even if the bioink started perfectly mixed. • That settling shows up in ways anyone running a bioprinter will recognize. • Sunk cells can increase the chance of clogs, create uneven cell density within a printed structure, and make one print differ from the next for reasons that are hard to diagnose.
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